Furnace construction



Patented Mar. `12, 19219.

UNITED STATEs y N1,704,902 PATENT OFFICE.

WILHELM EoHN, or HANAU0NTHEMATN, GERMANY, AssreNoB. `To THE Flam' vAcUUm'scHMELzE GESELLSCHAFT MIT EESCHRNKTEE. HAETUNG, or FRANK- EUHNACE CONSTRUCTION.'

Application filed December 12; 1924, Serial No. 755,480, and in Germany December 24, 1923.

My invention refers to furnaces and mora especially to means whereby the hearths and other parts including the shafts of furnaces of all sorts including reheating furnaces can bey made and constructed in an easierv and more effective manner than has hitherto been possible.. .y

' vAs is well knownto persons skilled in the art, the hearths of metallurgical yfurnaces such as the open hearth furnaces, the hearths of electric arc furnaces, and the hearths and the heating rings of induction furnaces 'are constructed at present in a great many cases i by moistening or stirring thercfractory material with water, tar or other more or less viscous liquids, with or without the use of a template, and thereafter stamping it. This method involves the drawback that a hearth ,made in this manner must be iirst dried with great care and then slowly heated up and burnt. Frequently the last traces of moisture are removed only during the first metallurgical operation.' The products of evaporation react with the chargeand frequently .spoil it so that the normal quality of the charge is attained only after several charges have been worked.

`The novel mode of proceeding according to the present invention .allows employing refractory granular masses in dry state for `the construction of irefractory .hearths without adding any moistening agent nor any means for imparting plasticity to the massf In practicing my invention I may for instance proceed as follows -I first place in the furnace a body forming a template and consisting `of a material capable of retaining its form during the period of construction, for instance a sheet metal or cast metal template. This bod Vremains in the hearth and is ultimately melted down together withV the charge inthe first melting operation; its outward shape predetermines the form of the hearth, heating ring or the like to be constructed. Underneath and around this template I simply throw in the refractory material which may consist of pure quartz sand, pure alumina, magnesite or some other re' fr actory substance. If the furnace, such as for instance an induction furnace, is then started operating in the wellknown manner,

the first charge' being for instance filled directly into the template and carejbeing taken to maintain forsome time a temperature only the temperature be then raised 'further and the charge is melted down, the fritted heating rin g or hearth will keep its form and after pouring the first charge the second can at once be introduced in the fritted ring or hearth which is now sufficiently strong.

If the working temperature of the furnace 1s low or if the refractory Vmaterial used does not sinter or frit at a temperature slightly be` low the working temperature, fritting of the material will still take place if according to the present invention a small percentage of products capable of sintering is added in finely powdered form.' Of products adapted for use in such cases and which will be chosen in each individual case in accordance with the vspecial purpose to which the furnace is used, the following are named by way of examplez-powdered glass, ground iron oXid, ground slag, boric acid, silicates, borates and kindred products. The quantity of such products to be added varies according to the purpose' in question, the nature of the refractory material and the working temperature ultimately employed. The possible combinations are so numerous that it is impossible to enumerate them. I will however illustrate my invention by giving a few examples of how it is practiced.

For instance a hearth for melting copper or alloys such as constantan or nickelin is preferably made from pure suitably grained quartz sand. However such sand'will not frit or sinter ofitself at the temperatures at which these metals or alloys melt, and I therefore add to it for instance about 2% powdered glass or 3% b oric acid. The. same kind of sand is Apreferably used for hearths designed for melting pure iron alloys and more especially silicon-containing to be rolled into sheets for use in transformer construecan be made. Pure fused alumina or fused.-

bauxite such as are used for grinding purposes may be used where the charge is a high grade refractory'lining for specially high grade steel. Either material possesses the further advantage of not notably reacting with the carbon in the steel, contrasting with a silica or a magnesite lining which reacts vigorously with the steel, entailing a loss of carbon. Pure fused aluminal is also capable of sintering at a temperature slightly below the melting point of the charge. -If it be desired -to obtain a particularly well sintered hearth, a fiux such as lnentioned above, should be added here also. Y

Particular advantages are derived from the new method in repairing damaged or cracked refractory linings or hearths. If one tries to patch them up with pasty materials, it is impossible to fill narrow fissures down to the ground and in such cases the .cracks must either be widened artificially or else theycan be mended only superficially and the'cracks will open again later on.' The dry materials employed in accordance with the present invention can simply be caused to dribble into the cracks in such manner as to completely fill them. They are prevented from dribbling out into the hearth by superficially clogging or luting the crack with some'suitable material, or, better still, by closing the opening of the crack by means of a sheet metal strip.

Hearths constructed in accordance with the present invention involve the advantage of having much less -tendency to crack than hearths stamped from moist or plastic refractory material, and farv less time is consumed `in their construction.

In the'drawings affixed tothis specification and forming part thereof several furnaces embodying my invention are illustrated dia-1 grammatically'by way of example.

Fig. 1 is a section of a shaft furnace of the cupola furnace type, l

Fig. 2 is a similar 'view of the hearth -of a Heroult furnace, and

Fig. 3 is a section of-an induction furnace.

Referring to Fig.-1 of the drawings, 1 is a sheet iron tube serving as a template andl 2 is the outer wall. The clearance between the two is tilled with a granular refractory material 3. In order to form the hearth, this furnace is filled with coke '6 which -is then brought to red heat, thereby causin that part of the granular material which a joins the template 1, to sinter and frit. I may however also pass an electric current through the template, thereby'heating it to red heat to cause the granularmaterial to sinter and frit, which the template itself will melt down.

In the furnace shown in Fig.' 2 the teme plate 1 has the form of a trough. is the granular material. I may cause sintering -and fritting of this material by entering the first charge inthe trough and slowly smelting it, or else the trough is lled with coke 6, an electrode is placed on the coke and electric current is supplied to heat the coke to a temperature where the granular material will sinter and frit.

In the, induction furnace illustrated in Fig. 3, 2l is the outer wall and 1b is a channel.- shaped sheet metal ring forming the template, while' 3" and 4" are the granular refractory material placed under and around it' and 5 is the transformer iron. By introducing into this annular channel the rst charge 6l and heating same the adjoining part ofthe material will sinter and' frit and thus form the groove.

I wish it to be understood that I do not desire to be limited to the exact kinds and quantities of material nor to the particular operavtions described, except as dened in the claims, for obvious modifications will occur to a person skilled in the art.

I claim 1. Ihe method of making the hearths,

'heating rings, or the like in metallurgical and other furnaces, comprising placing in the furnace a metal template, pouring around andv below said template a dry Lgranular refractory material the particles of which are.y

freely movable relative to each other, placing a charge in the template and heating it therein up to a temperature suficing to cause sintering and fritting of the refractory ymaterial adjoining the template and thereafter to melt the template and its contents.

2'. The method of making the hearths, heating rings, or the liker in metallurgical and other furnaces comprising placing in the furnace a metal template, pouring around4 and below said template a mixturel of dry granular refractory material the particles 'of which are freely-movable relative to each other and a small quantity of a finely divided material capable of reducing the sintering 'temperature of the-refractory material, plac- 'ing a charge in the template and heating it therein up to a temperature suiiicing to c ausesintering and fritting of the mixture ad]oin ing'the template and thereafter to melt the template and its contents.

3. A metallurgical furnace comprising an outer wall, an inner metal template having a melting point below the intended temperature of the charge, and a dry finely divided granular refractory material adapted to sinter at a temperature below the melting temperature of the template filling the interstice between said wall and said template.

In testimony whereof I atlix my signature.

WILHELM ROI-DW. 

